The invention concerns an intake pipe arrangement for a multi-cylinder internal combustion engine with fuel injection nozzles, whereby each cylinder of the engine is connected by way of a first intake pipe, which is designed for optimal filling in a low air throughput range, with a first intake manifold and by way of a second intake pipe designed with lower resistance with a second intake manifold, each of which intake manifolds is preceded by a throttle member. The throttle member of the first intake manifold opens already in the lower air throughput range whereas the throttle member of the second intake manifold additionally opens only in a higher air throughput range. In the intake pipe arrangement of this kind known from EP application No. 0 098 543, F02B 27/00, the long and thin first intake pipes which extend with a curvature of 180.degree. open into the second intake pipes, which are relatively short and have a considerably larger flow cross section, ahead of the entry thereof into the cylinder block or cylinder head so that the second intake pipes in order to achieve the large flow cross section must be provided with relatively large cross dimensions. The successive intake ports in the cylinder block or cylinder head also requiring large cross dimensions. In this known engine, the injection nozzles are located, in the direction of flow, behind the point of discharge of the first intake 10 pipes in the intake ports. Due to the fact that only one intake nozzle is provided per cylinder and the two intake pipes are arranged coaxially in the vicinity of the intake valve, the intake valve, in order to attain a sufficient flow cross section, must be of very large size, which for reasons of space creates difficulties. The known internal combustion engine also suffers from the disadvantage that one fuel injection nozzle per cylinder must be controllable over the entire range of fuel requirements from idling to the highest load. This causes difficulties, in particular as concerns a precise fuel apportionment during idling, inasmuch as then injection pulses which are very short are needed and even the slightest tolerances lead to relatively large deviations between the actual quantity and the desired quantity of the apportioned fuel.
From DE-OS 15 76 230, F02B 27/00, for example, is also known a piston internal combustion engine whose two intake pipes, likewise dimensioned for optimal filling in various speed and load ranges, are connected by means of individual intake valves with the cylinders concerned. However, this publication does not contain any information on details, such as intake manifolds, arrangement of fuel injection nozzles and throttle organs serving as power control elements.
The intake device as per DE-OS 35 02 699, F02B 27/00, too, has two intake pipes per cylinder, which intake pipes by means of intake valves with possibly different control times, are in connection with the combustion chamber concerned. On the input side, both intake pipes which evidently are rendered identical, are associated with a device for adjustment of their length to the prevailing operating states. An injection nozzle is lodged in a cavity in the partition between the two intake pipes each of which is associated with one cylinder or said nozzle is provided individually in each intake pipe. By means of a throttle valve in one of the intake pipes it is obtained that the intake pipe opens only in a medium speed range. If one adheres to the separation of the two intake pipes, which is of advantage from the point of view of fluid mechanics, this construction requires a large effort in the form of injection nozzles due to the arrangement of individual fuel injection nozzles in each of the intake pipes.
With a view to rounding out the state of the art, reference is also made to DE-OS 35 19 143, F02D 9/02 which discloses a reciprocating-piston internal combustion engine with two identically shaped intake pipes and intake valves per cylinder. With each of the intake pipes of all the cylinders is associated a common intake line arrangement whereby in each intake line arrangement is placed a throttle valve. The throttle valves are actuated in sequence in the manner of a register. It is stated that if the engine in question operates with fuel injection, injection nozzles may be arranged either in the intake line arrangements (central injection) or in the intake pipes (single intake pipe injection). In the former case, idling difficulties may occur, in particular when the engine is cold, in that the fuel delivery takes place relatively far from the intake valves. Moreover, here, again, difficulties related to precise fuel quantity metering arise over the entire control range. The latter case is characterized by a large expenditure for injection nozzles.